Cotton is an important fiber crop. Breeding and biotechnology have been applied to cotton to improve its agronomic traits and the quality of the product. One such agronomic trait is resistance to insects, the advantages of which are readily apparent. Genes encoding insecticidal proteins have been introduced into cotton plants. In order to alleviate any concern that a given type of insect could develop resistance to a single type of insecticidal protein, plants are often developed that produce two different types of insecticidal proteins. Thus, the odds of an insect being hypothetically capable of developing resistance to two different insecticidal proteins are extremely low.
Cry1Ac insecticidal proteins and genes are known in the art. See, e.g., U.S. Pat. Nos. 6,114,138; 5,710,020; 6,251,656; and 6,229,004. Cry1F insecticidal proteins and genes are also known in the art. See, e.g., U.S. Pat. Nos. 5,188,960; 5,691,308; 6,096,708; and 6,573,240.
The expression of foreign genes in plants is influenced by where the foreign gene is inserted in the chromosome. This could be due to chromatin structure (e.g., heterochromatin) or the proximity of transcriptional regulation elements (e.g., enhancers) close to the integration site (Weising et al., Ann. Rev. Genet 22:421–477, 1988). For example, the same gene in the same type of transgenic plant (or other organism) can exhibit a wide variation in expression level amongst different events. There may also be differences in spatial or temporal patterns of expression. For example, differences in the relative expression of a transgene in various plant tissues may not correspond to the patterns expected from transcriptional regulatory elements present in the introduced gene construct.
Thus, it is necessary to create and screen a large number of events in order to identify an event that optimally expresses an introduced gene of interest. For commercial purposes, it is common to produce hundreds to thousands of different events and to screen those events for a single event that has desired transgene expression levels and patterns. An event that has desired levels and/or patterns of transgene expression is useful for introgressing the transgene into other genetic backgrounds by sexual outcrossing using conventional breeding methods. Progeny of such crosses maintain the transgene expression characteristics of the original transformant. This strategy is used to ensure reliable gene expression in a number of varieties that are well adapted to local growing conditions.
It would be advantageous to be able to detect the presence of a particular event in order to determine whether progeny of a sexual cross contain a transgene of interest. In addition, a method for detecting a particular event would be helpful for complying with regulations requiring the pre-market approval and labeling of foods derived from recombinant crop plants, for example. It is possible to detect the presence of a transgene by any well-known nucleic acid detection method such as polymerase chain reaction (PCR) or DNA hybridization using nucleic acid probes. These detection methods generally focus on frequently used genetic elements, such as promoters, terminators, marker genes, and the like. As a result, such methods may not be useful for discriminating between different events, particularly those produced using the same DNA construct, unless the sequence of chromosomal DNA adjacent to the inserted DNA (“flanking DNA”) is known. An event-specific PCR assay is discussed, for example, by Windels et al. (Med. Fac. Landbouww, Univ. Gent 64/5b:459462, 1999). This related to the identification of glyphosate tolerant soybean event 40-3-2 by PCR using a primer set spanning the junction between the insert and flanking DNA. More specifically, one primer included sequence from the insert and a second primer included sequence from flanking DNA.
U.S. patent application Ser. Nos. 20020120964 A1 and 20040009504 A1 relate to cotton event PV-GHGT07(1445) and compositions and methods for the detection thereof. WO 02/100163 relates to cotton event MONI5985 and compositions and methods for the detection thereof. WO 2004/011601 relates to corn event MON863 plants and compositions and methods for the detection thereof. WO 2004/072235 relates to cotton event MON 88913 and compositions and methods for the detection thereof.
However, no such procedures and materials were specifically known, heretofore, that could be used to specifically identify Cry1F and/or Cry1Ac stacked cotton as discussed below.